The present invention relates to an apparatus for checking for the presence of objects and in particular containers. In the beverage-producing industry, it is customary for beverage containers to be produced, filled, labelled and further treated in a multiple-unit process. In this case, the containers are transported for example by means of rotary starwheels from one treatment unit to a further treatment unit. It is often necessary to check whether a container is in actual fact arranged in a certain position, for example whether a certain gripping clamp is occupied by a container. If a gripping clamp for example is not occupied by a container, this may lead to the situation whereby a beverage is filled into a container that does not exist and therefore soiling of the installation occurs.
It is known in the prior art to use ultrasound elements to check whether certain gripping clamps are occupied by containers. For this purpose, there is usually provided an ultrasound transmitter and also an ultrasound receiver, and the gripping clamps holding the containers to be treated are transported between these two units.
If a container is present in a certain position, the signal transmission from the ultrasound transmitter to the ultrasound receiver is interrupted and in this way the state of occupancy of the corresponding gripping element can be checked.
The sensors known to date as the prior art are usually made from plastics, such as Teflon for example. The ultrasound transmitter has a loudspeaker on its outer region, and the receiver accordingly has a microphone which picks up the sound signal from the transmitter. Particularly in applications in the so-called clean-room sector, in some cases considerable external treatments with further liquid and gaseous media take place. This often leads to failures of the transmitting and receiving units and requires inter alia an intervention in the sterile area in order to dry the sensors.
The object of the present invention is therefore to provide an apparatus for checking for the presence of objects, in particular containers, which particularly in critical environments, such as clean-room areas for example, is less susceptible to substances such as cleaning gases for example.